Abstract

Semileptonic (B) over bar decays to DXl (nu) over bar (l = e or mu) are selected by reconstructing D(0)l and D(+)l combinations from a sample of 230 x 10(6) Y(4S) --> B (B) over bar decays recorded with the BABAR detector at the PEP-II e(+)e(-) collider at SLAC. A global fit to these samples in a three-dimensional space of kinematic variables is used to determine the branching fractions B(B- --> D(0)l (nu) over bar = (2.34 +/- 0.03 +/- 0.13)% and B(B- --> D*(0)l (nu) over bar) = (5.40 +/- 0.02 +/- 0.21)% where the errors are statistical and systematic, respectively. The fit also determines form-factor parameters in a parametrization based on heavy quark effective theory, resulting in rho(2)(D) = 1.20 +/- 0.04 +/- 0.07 for (B) over bar --> Dl (nu) over bar and rho(2)(D*) = 1.22 +/- 0.02 +/- 0.07 for (B) over bar --> D*(0)l (nu) over bar. These values are used to obtain the product of the Cabibbo-Kobayashi-Maskawa matrix element |V-cb| times the form factor at the zero recoil point for both (B) over bar --> Dl (nu) over bar decays, G(1)|V-cb| = (43.1 +/- 0.8 +/- 2.3) x 10(-3), and for (B) over bar --> D*l (nu) over bar decays, F(1)|V-cb| = (35.9) +/- 0.2 +/- 1.2) x 10(-3).